The present application claims priority under 35 U.S.C. xc2xa7371 from PCT Application No. PCT/EP00/06951, filed on Jul. 20, 2000, which claims the benefit of German Application Serial No. 19938345.6, filed on Aug. 13, 1999, the disclosures of which are incorporated by reference herein in their entireties.
1. Field of the Invention
The present invention relates to a method and apparatus for detecting the position of a vehicle in a predetermined area, in particular a storage facility, and to a store management method and system.
2. Background of the Invention
DE 4429016 A1 discloses an apparatus and a method for navigation of driverless vehicles. In this case, the magnitude and angle of incremental movements from the motion of the vehicle are detected by means of an integrated navigation apparatus. Furthermore, a respective reference position of the vehicle is fixed automatically at predetermined points within a pre-determined area by means of a CCD camera whenever the vehicle passes an appropriate point. Furthermore, the current position of the vehicle in the predetermined area is detected by vectorial summation of the detected incremental motion vectors by means of an evaluation unit, to form the position vector related to the current reference position. The position and orientation identification described there are disadvantageously derived from a very expensive CCD camera and a high-contrast lighting means in the form of a ceiling lamp. Failure of the lamp leads to loss of position.
DE 3490712 C2 discloses a vehicle control and management system with a movement drive device for driving the vehicle, a steering device for controlling the route of the vehicle, an integrated navigation device for calculating the position of the vehicle track on an incremental basis, a device for saving a desired route for the vehicle, a device for controlling the vehicle drive and steering device in order to drive the vehicle along the desired route, and a device for saving the position of one or more fixed-position reference destinations.
DE 3538908 A1 discloses an autonomous on-board position-finding system for position determination and collision protection fox robot vehicles and industrial trucks, based on the integrated navigation method, on predetermined routes. The current width and length are determined continuously, by means of an addition circuit, using at least one distance sensor within the system. These sensor values are processed in such a way that a control signal is produced to guide the vehicle safely along the center of the route.
DE 4039887 A1 discloses a further known vehicle management and destination routing system.
Although it can be applied to any desired vehicles and areas, the present invention, as well as the problems on which it is based, will be explained with respect to two forklift trucks in a storage facility, as components of a store management system.
A store management system monitors, controls, documents and analyses the movement of goods in a storage depot. Transport vehicles, such as forklift trucks, are normally used for moving the goods.
Important factors which reflect the quality of such a system are the access times, the acquisition times and the accuracy with which storage locations are determined.
By way of example, one known system uses fixed predetermined routes for transportation vehicles, for example on rails, and position sensors installed on them.
The above known approach has been found to have the disadvantage that only predetermined routes can be used, and installation and retrofitting involve a need for complex changes to the system.
A system with non-contacting position detection, such as the known GPS system (Global Positioning system) would be more expedient. The positions which occur in the storage areas and which need to be classified are, however, in the range of centimeters or less (for example in the region of 40 cm for European standard pallets). Such high position resolution cannot be achieved, however, with the known differential GPS system whose resolution capability is typically only about 1 m. Furthermore, the GPS system cannot be used within closed rooms, owing to the shielding effects.
One object of the present invention is thus to provide a method and apparatus for detecting the position of a vehicle in a predetermined area, in particular a storage facility, which allows more accurate and more reliable position findings, and which requires only minor changes to the area, or the storage areas. A further object is to provide a storage management method and system.
The method according to the invention and having the features of claim 1, as well as the corresponding apparatus as claimed in claim 6, have, in contrast to the known solution approach, the advantage that they allow highly accurate and reliable position finding, and require little in the way of changes to the existing area or storage areas. Retrofitting is thus feasible without any problems, in addition to initial equipment.
The idea on which the present invention is based is to automatically fix a respective reference position of the respective vehicle at predetermined points within the predetermined area whenever the vehicle passes a corresponding point. The automatic fixing of a respective reference position of the vehicle at the predetermined points is carried out by means of a second sensor device, which is fitted to the vehicle and interacts, in a non-contacting manner, with a respective reference marking at the corresponding point within he predetermined area. The Respective reference marking has reflective and non-reflective areas, which the vehicle scans simultaneously by means of two signals, with the coordinates of the reference position and, optionally, the through-movement angle being determined by evaluating the tire profile of the reflected intensity of the signals.
The dependent claims relate to advantageous developments and improvements of the respective subject matter of the invention.
According to one preferred development, the signal carriers are light beams, preferably laser beams, or magnetic induction lines of force.
According to a further preferred embodiment, the respective reference marking has a rectangular strip, which has two reflective areas and one non-reflective area along the rectangle diagonals, under which the vehicle moves. This reference marking advantageously allows an analytical solution for determination of the coordinates of the reference position and of the two-movement angle by evaluating the time profile of e reflected intensity of the signals.
According to a further preferred development the magnitude and the angle of incremental motion vectors relating to the movement of the vehicle are detected by means of a first sensor device, which is fitted to the vehicle. This preferably comprises a gyrator for angle determination and an encoder for length determination.
According to a further preferred development, the automatic fixing of a respective reference position of the vehicle is carried out such that the statistical discrepancy between the detected current position and the actual position does not exceed a predetermined limit value.